1. Field of the Invention
This invention relates to interlocking roofing panels, and more particularly to metal roofing panels.
2. General Discussion of the Background
It has long been known that the roof of a structure can be protected by roofing materials such as asphalt, slate, or metal. U.S. Pat. No. 2,873,699, for example, shows a metal roof which includes a series of side-by-side roofing panels which have interlocking edges that slide one into the other. Each panel is held to a roof board by inserting a nail through the panel into the board. The adjoining interlocking panel covers the nail head to protect it and inhibit moisture from seeping through the nail hole to the roof board. Such an arrangement does not completely prevent seepage of water through the nail hole and into the roof board because the interlocking ridges of the panels fit snugly, one within the other, and capillary action allows water to move between them to the region of the nail head.
U.S. Pat. No. 3,495,363 attempted to overcome the problem presented by capillary movement of water between interlocking ridges of adjoining panels. The outer interlocking ridge was made much larger than the inner ridge such that the inner ridge formed a dam between the nail head and the edge of the larger ridge which was exposed to environmental moisutre. The inner and outer ridges, however, were still close enough together that capillary action permitted movement of water between the ridges, over the dam, and to the nail head, whence water moved through the panel into the roof board.
U.S. Pat. Nos. 3,606,720 and 4,400,922 both show interlocking roofing panels. Neither of the foregoing interlocking roofing panels can adequately interrupt capillary flow of water between the interlocking ridges of the panels to prevent seepage of moisture through the nail holes of the panels to the underlying roof board.
Yet another drawback with roofing systems such as those shown in U.S. Pat. Nos. 3,495,363 and 3,606,720 is that each panel is secured to an underlying structure with a nail or screw which pierces the panel and fixes it rigidly to the structure. The hole produced by piercing the panel provides a site through which moisture can pass to the underlying structure. Moreover, the rigid attachment site does not accommodate normal expansion and contraction of the panel in response to changing environmental temperatures. The panel therefore buckles and cracks.
It is accordingly a primary object of this invention to provide a roofing structure which prevents moisture on a roof from entering joints and seeping beneath roofing panels.
It is another primary object of this invention to provide a roofing structure which can expand and contract in response to changing environmental temperatures without buckling or popping.
It is yet another primary object of the invention to provide such a roofing structure which is easy and convenient to install.